The escalating demands for high density and performance associated with ultra large scale integration semiconductor devices require a design rule of 0.25 microns and under, such as 0.18 microns, increased transistor and circuit speeds, high reliability and increased manufacturing throughput. The reduction of design rules to 0.25 microns and under generates significant challenges to the limitations of conventional interconnection technology, including conventional photolithographic, etching and deposition techniques.
Hydrogen silsesquioxane (HSQ) offers many advantages for use in interconnect patterns as a dielectric layer. HSQ is a highly desirable dielectric material. One form of HSQ is commercially available from Dow Corning Corp. under the product name Flowable Oxide.TM. or FO.sub.x .TM.. However, the use of HSQ presents problems, particularly when plasma etching is conducted. When a photoresist mask is deposited and the through-hole is etched to expose a portion of the HSQ layer, the photoresist mask is then stripped, typically employing an oxygen 02-containing plasma. Assessments of the feasibility of employing HSQ as a dielectric layer in interconnection patterns revealed that the O.sub.2 -containing plasma employed to strip the photoresist mask degraded the HSQ layer.
HSQ typically contains between about 70% and about 90% Si-H bonds. However, upon exposure to an O.sub.2 -containing plasma, a considerable number Si-H bonds are broken and Si-OH bonds are formed. Upon treatment with an O.sub.2 -containing plasma, as much as about 20% to about 30% of the Si-H bonds in the deposited HSQ film remained. In addition, exposure to an O.sub.2 -containing plasma increased the moisture content of the deposited HSQ film and its propensity to absorb moisture. An HSQ film having reduced Si-H bonds and high Si-OH bonds tends to absorb moisture from the ambient, which moisture outgases during subsequent barrier metal deposition. Thus, during subsequent barrier and metal deposition, outgasing occurs thereby creating voids leading to incomplete electrical connection.
In copending application Ser. No. 08/951,592, filed on Oct. 16, 1997 (Our Docket No. 50100-695), a method is disclosed for restoring degradation of an HSQ film by exposure to an H.sub.2 -containing plasma to increase the number of Si-H bonds, to decrease the number of Si-OH bonds, and to decrease the propensity to absorb moisture. The disclosed treatment with an H.sub.2 -containing plasma enables the use of HSQ to gap fill metal lines and form borderless vias with improved reliability by reducing outgassing and, hence, void formation.
In view of the manifest advantages of HSQ, there exists a need to provide technology whereby HSQ can be employed as a dielectric layer in forming interconnection patterns in a semiconductor device. There also exists a need to form interconnection patterns employing HSQ as a dielectric layer with improved reliability and increased production throughput.